This invention relates to electrical equipment and, in particular, to an apparatus and method of detecting authorized removal of such electrical equipment.
Advancements in the field of electronics have resulted in a significant reduction in the size of electrical components. This permits the design of small, very complex and often very costly pieces of equipment. Such advancements are advantageous in that modern equipment is more transportable and requires less space on a desk or workstation. However, the smaller the equipment, the more difficult it becomes to secure it against theft. For example, a computer of 5 years ago was too large for an employee to walk unnoticed out of a building with. Today, thousands of dollars, and sometimes tens of thousands of dollars, worth of computer equipment may be placed in a single brief case and carried out of a building. Furthermore, once stolen, smaller equipment is easier for the thief to hide and dispose of. There does not appear to be an end in sight to the increased miniaturization of advanced electronic devices and, therefore, the need for theft protection will increase.
For electrical equipment in use today, a variety of methods of securing the equipment are available. First, for computers, a special electronic card may be designed to install inside the computer. The card responds to polls from an external monitoring station. When the computer, and therefore the card, is removed, the card stops responding to the polling of the central station and an alarm is initiated. However, major disadvantages to this method exist in that not all computers are compatible with the electronic card, the electronic card may not be used in the computer peripheral devices such as printers and monitors, and the card may be expensive.
A second method of protection is to wire a pressure sensor or micro-switch into the computer which causes a local alarm to sound when the computer is moved. This also is disadvantageous because it requires incorporating these components into the computer.
A third method of protection is to place a non-removable tag on or in each piece of equipment. A sensing device, responsive to the presence of the tag, is situated at each exit point of the premises. If an attempt is made to move equipment containing a tag past a sensing device, an alarm will be initiated. The disadvantage of this method is readily apparent in locations having multiple exit points. Each exit point requires a costly sensing device.
A fourth method of protecting electrical equipment is described in U.S. Pat. No. 4,390,868. In this method, the cable connecting the equipment to the electrical power source is modified to include two light transmitting channels extending through the cable and two light sources at the end of the cable that plugs into the wall. The equipment to be protected is specially modified with two light sensors so that it will only operate when the special cable with its two light channels is present. The special cable is then non-removably affixed at the location where the equipment is to be used. It is assumed that the equipment will not be stolen because of difficulty in obtaining an equivalent cable. However, this method of deterrence will only work with equipment that is specially modified. Further, if the deterrence does not work and the equipment is actually taken, no alarm will be initiated.
It is therefore an object of the present invention to provide an apparatus and method by which electrical equipment may be protected from theft.
It is a further object of the present invention to provide a cable adapted to standard electrical equipment so that removal of equipment by unplugging or cutting of the cable is detected.
It is still a further object of the present invention to provide an apparatus and method for detecting removal of electrical equipment and transmitting such information to a central location through the existing AC power lines so that no separate wiring is necessary.